The present invention relates to a priming and self-destruct system of a munition, and in particular, to a submunition that rotates around the longitudinal axis of and is designed to be ejected from a cargo shell.
As is well-known in the art, a munition is comprised of a generally cylindrical body that holds the war charge. This body is topped with a casing-box which houses a Safety and Arming Unit (SAU) that comprises the priming and self-destruct system of the munition.
In real terms, the slide which carries the priming system of the charge is housed in the part of the casing box which is next to the war charge, whereas the impact detector is mounted in the other part of the casing box.
The impact detector typically comprises a screw wherein one end is linked to a ribbon-parachute and the other carries the main firing pin. The screw is aligned along the longitudinal axis of the munition and is screwed through a nut that is movable through inertia in a bore hole in the casing box. When the slide is in the safety position, the main firing pin does not lie on the axis of the priming system, but it is often used to lock the slide in the safety position.
Under normal use, e.g., after the munition has been ejected from the cargo shell, the ribbon parachute is deployed to stabilize the trajectory and direct the orientation of the munition as it falls to the ground. The deployment of its ribbon-parachute, combined with the munition's rotation about the longitudinal axis (which is imparted because of the rifling in the barrel), causes a relative displacement of the impact detector screw with respect to the nut in a direction tending to separate the slide from the firing pin.
The slide thereby moves into the armed position, and the firing pin is once again aligned axially with the priming system. As the munition hits the ground, it becomes subjected to a strong deceleration, and the screw-nut assembly moves by inertia in the direction of the slide, and as a result the axial percussion of the priming system is effected by the firing pin (integrally formed with the screw) thereby causing the munition to explode instantaneously.
Generally, the impact detector functions more effectively if it is aligned with the longitudinal axis of the munition. In other words, if the trajectory of the munition at the moment of its impact with the ground corresponds roughly to this axis, there is a great probability that the system will function instantaneously.
In real terms, these optimum conditions are not always fulfilled, often due to the misfunctioning of the ribbon-parachute. If the trajectory of the munition is not correctly stabilized as it falls, it may hit the ground in a direction that hampers the correct functioning of the firing pin. Even if the munition does not detonate instantaneously, it is still dangerous.
To reduce this type of misfunctioning as the munition hits the ground, it is known to add a second function mode to the priming system that operates by self-destruction and enables the munition to be neutralized on the ground. This second function is generally operated by a delay pyrotechnic train initiated by a secondary firing pin.
In U.S. Pat. No. 4,811,664, the secondary firing pin is of the centrifugal type. It performs a pivotal movement under the effect of the rotation of the munition. Once the slide valve has moved into its armed position, a pyrotechnic delay period begins to run. The delay is calculated to be greater than the time taken by the munition to reach the ground. Once the delay period terminates, the priming system is initiated.
The solutions which use a pyrotechnic delay are nevertheless costly, and an object of the invention is to design a purely mechanical self-destruct system comprising a minimum number of elements that is also reliable and easy to implement.